1. Field of the Invention
This invention relates to robotic feeders in general and particularly as directed to a system whereby a part is transferred from a location outside of the work envelope of an industrial manipulator to a location within the work envelope. This invention further includes a part centering device disposed within the work envelope and adapted to center the part delivered thereto about a centerline of the part defined by the X and Y axis thereof. This system can transport various sizes and shapes of material into the work envelope and center that material regardless of its size and shape thus permitting an accurate and repeatable acquisition by the robot.
2. Description of the Prior Art
The general acceptance of industry automation as an essential requirement for improving productivity has increased the acceptance level of the robot or industrial manipulator apparatus as a mechanism for achieving automated industrial applications. The acceptance of robots as a useful, industrial "tool" has resulted in a marked demand for robotic systems capable of implementing what have heretofore been either difficult, dangerous or tedious tasks.
The automotive industry presents exceptional opportunities for the use of robots or industrial manipulators for the purpose of improving productivity and enhancing quality of the finished product. What were once routine tasks are now efficiently and effectively being implemented by robots working side by side with their human worker counterparts. For example, robots are now used to apply adhesives and sealing materials to various component parts of an automobile. Robots are also used to move heavy component parts and weld the various component parts of an automobile together as well as applying the final coating of paint to the automobile. Certain tasks, however, have heretofore not lent themselves to automation. One example of such a task is the insertion or decking of windshields into vehicles. Several obvious factors have prohibited the automation of the decking process. A high level of accuracy is necessary in order to place the somewhat fragile windsheld into the windshield opening of the vehicle. A slight miscalculation during the decking process can result in damage to both the vehicle and possible destruction of the windshield. Additionally, the existing conveyors which transport the automobile through the various work stations in an automobile assembly facility are relatively unstable and tend to cause a slight change in the orientation of the vehicle mounted thereon. Moreover, typically the nearly complete vehicle into which the windshield is to be inserted is positioned on the conveyor apparatus in such a way as to render the exact location of the windshield opening to be consistently unknown. In other words, there is a certain level of random orientation of the vehicle on the assembly line during the stage in which the windshield is to be inserted. As a result, the decking operation has heretofore been accomplished through the use of two or more workmen engaging a windshield with handheld lifting equipment and walking across the assembly line so that one worker is along either side of the vehicle. The windsheld is then manually inserted into the windshield opening. During this process, workmen on either side of the vehicle walk alongside the vehicle as it passes through the windshield insertion station to match the speed of the vehicle and then insert the windshield. This technique does have the advantage of effecting windshield placement, while permitting the existing conveyor system to continuously transport the vehicle through the decking station.
In order to effect the automated insertion of a component part into a product, it is necessary to initially know both the exact orientation and location of the component part as well as the exact orientation and location of the product into which that part is to be inserted. With this information, the orientation of a component part can be established and once acquired by an industrial manipulator, the insertion of the component part into the product can be easily and quickly accomplished. Thus, in a robotic assembly or material handling system, the placement accuracy of parts or components is not only a function of robot repeatability but is directly proportional to the position of the part when it is picked up by the robot. Typically, manually loaded fixtures or mechanical devices are used to bias parts against two perpendicular sides of the component part. However, when such a technique is utilized, variations in size or shape from one component to another will cause the position of the component to change with respect to the pickup position of the robot arm. Man-to-machine interface of such devices can also be extremely dangerous since loading the fixture in which the component part is centered requires entry into the robot work zone.
Several schemes have been suggested for devices which can improve part placement in robotic assembly in handling systems. For example, mechanical alignment mechanisms have been added directly to a gripper. This technique will generally dedicate the gripper to a specific component part. Moreover, the additional weight of the alignment mechanism to the gripper assembly reduces the load carrying capacity of the robot. It has also been suggested that external sensors such as vision, sonic, etc. be employed to define the size, shape and location of the part and that the gripper orientation be adjusted for part pickup. This method, unfortunately, requires an increased cost and system complexity not to mention the fact that the accuracy obtained thereby can be limited. It has also been suggested that the part or component design be modified in order to render the part self-locating. This technique, when feasible, is limited to the amount of mismatch that is possible and may require compromises in both the appearance or functionality of the completed assembly.
It is, therefore, an object of this invention to provide a robotic part presentation station which offers a unique solution to the difficulties incurred during part pickup and placement.
It is a further object of this invention to provide a centering device upon which a workpiece can be centered about a central line in the X and Y axes direction of that workpiece. This provides an accurate location with respect to a programmable pickup point for acquisition by an industrial manipulator independent of the size and shape of the object being centered.
It is another object of this invention to provide a system whereby a component part can either be manually loaded or interfaced with a conveyor, counterbalanced stack of parts, indexing scissors table or similar such device to provide totally automatic parts feeding.
It is yet another object of this invention to provide a robotic part presentation station which transports the component part into the work envelope, permitting man-robot interface without the need for the man to enter or reach into the work envelope of the robot.
It remains another object of this invention to provide a device which has centering action that will occur on any part that can fit in the nest defined therein and is larger than the minimum nest opening of the device. Moreover, the range of part sizes that the nest will accept can be large and can be expanded by increasing the stroke of the centering arms. This centering station will center all parts that are symmetric in shape about the X and Y axes.